The mystery of how some dinosaurs got to be so big is closer to being solved

We know that dinosaurs like Brontosaurus were the largest creatures ever to walk the earth. Weighing in at up to 90 tonnes these massive beasts are something of a mystery because their ancestors are far smaller.

And this is where a 185-million-year-old dinosaur called Sarahsaurus aurifontanalis comes in. It is thought that Sarahsaurus belonged to the set of dinosaurs that predated the sauropods.

There are also excellent quality remains for Sarahsaurus which has allowed paleontologists a much clearer look at its anatomy and how it relates to is larger cousins.

Adam Marsh, a paleontologist at Petrified Forest National Park, said "Sarahsaurus preserves in its anatomy the anatomical changes that were happening in the Late Triassic and Early Jurassic that were occurring in the evolutionary lineage".

Marsh continued: "It can help tell us how getting big happens".

Two specimens being studied were discovered in 1997 by Professor Timothy Rowe. While the skull was missing the remains are in very good condition overall.

Sarahsaurus was a ground-sloth-like creature that stood upright and walked on its hind legs. It had powerful forelimbs with curved claws on the first finger of each hand. It also demonstrates how later relations would increase their size and lengthen their neck vertebrae.

Marsh went on to say "We’ve got two individuals from basically the same hole in the ground with different bumps and grooves on their femora. It lends itself really well to this comprehensive anatomical description and it’s going to be really important for comparisons of early dinosaur anatomy".